This invention relates generally to roof ventilators, and particularly to improved methods for manufacturing a foldable corrugated plastic ridge cap type roof ventilator.
The preferred embodiment of a foldable corrugated plastic ridge cap roof ventilator is disclosed in U.S. Pat. No. 4,803,813 to Fiterman, the content of that patent disclosure and its related documents being incorporated herein by reference. The details and description of the fabrication, assembly, and use of the Fiterman '813 roof ventilator should be assumed to apply in all pertinent respects to the roof ventilator disclosed herein, with the exception of the particular variations and improvements set forth and described with particularity.
Several patents on roof ventilators are also of note, particularly U.S. Pat. No. 3,949,657 to Sells, discussed in the background of the Fireman '813 patent, and the improvement thereto disclosed in U.S. Pat. No. 4,843,953 to Sells. The Sells '657 roof ventilator is described as being fabricated from a section of honey-combed material coated with a moisture impervious substance, although the roof ventilator can be manufactured from a plurality of individual strips of corrugated plastic sheet material which are stacked and fastened together and then cut on the bias to produce the beveled inner and outer edge surfaces.
While one of the purposes of the narrow channels or tubular air passages of the roof ventilators identified above is to prevent snow or moisture from being blown upwardly from the exterior to the interior of the ventilator, as well as to prevent the ingress of insects, the tubular air passages can still allow precipitation drawn by capillary action or driven by high winds to reach the interior of the ventilator.
While flashing strips such as shown in the Sells '953 patent will assist in minimizing such problems, the angled flashing strip either requires separate assembly at the time of installation or prevents the incorporation of such a flashing strip in the manufacture of a foldable roof ventilator such as the Fiterman '813 patent discloses.
Another alternative is disclosed in U.S. Pat. No. 4,876,950 to Rudeen, which utilizes a single plastic membrane which flexes to conform to different roof pitches, and has a pair of open-celled foam plastic strips secured to the bottom surface thereof to act as the two vent parts placed on opposing sides of the open roof peak. The open celled foam consists of a latticework of interconnected filaments which permit ventilation, but which do not present a plurality of straight or unobstructed paths extending from the exterior to the interior of the roof ventilator.
While encompassing several distinctive features, the Rudeen '950 roof ventilator does lack the advantages of the Fiterman '813 roof ventilator in its unitary construction and ability to be folded. Where appropriate, however, the improvements disclosed herein apply equally to a roof ventilator construction of the type disclosed in the Rudeen '950 patent, as may be seen more fully from the detailed description of the invention set forth below.
One drawback of the foldable or flexible roof ventilators discussed above is that if the top surface of the top panel is to be angled parallel with the surface of the roof, the top panel must be scored or creased in order to form a center fold line across which the panel is folded or flexed to bring the top panel and opposing vent parts into parallel alignment and contact with the surface of the roof. Even with such a fold or crease, the top panel of the roof ventilator may not always fold along a straight line, but instead will buckle irregularly. Conversely, in some roofing applications (such as with the curved ceramic roofing tiles popular in the western United States) it is necessary to permit the top panel to be gradually convoluted rather than folded along a straight line, in order that the top panel will mold or conform to the non-uniform shape or arrangement of the roofing tiles.
Moreover, the top panel is generally solid throughout the central portion thereof to prevent moisture from leaking directly through the roof opening, and the top panel therefore does not permit or assist in ventilation between the interior and exterior of the roof ventilator.
Other screening or partitioning devices for blocking wind driven precipitation from entering the roof opening through the interior of a roof ventilator are known besides that shown in the Sells '953 patent. Representative examples are shown in U.S. Pat. No. 2,868,104 to Honholt; U.S. Pat. No. 3,311,047 to Smith; U.S. Pat. No. 3,481,263 to Belden; U.S. Pat. No. 3,625,134 to Smith; and U.S. Pat. No. 4,676,147 to Mankowski. The principle behind the operation of most of these devices is simply to place a perforated or slotted panel within the interior of the roof ventilator. The Mankowski '147 patent is interesting in that it places a generally open region between the exterior of the ventilator and the perforated panel, and a solid barrier of reduced height within that open area.
It must be noted that these examples all show roof ventilators constructed from generally heavier gauge materials such as sheet metal and require significantly greater fabrication time and more complex construction techniques than the foldable double-faced corrugated plastic or foam roof ventilators discussed above.